So, as someone that lived in New York for 6 years and California for 6 years, stories like this are incredibly depressing. The US is the world's largest economy and should be the shining example of amazing infrastructure, high-tech, green cities, and forward thinking policies. California is an especially egregious example in terms of infrastructure investment: If California was a country it would be the world's fifth…
Yeah I can: approximately nothing. What exactly would you do with such a train? Neither LA nor San Diego have meaningful downtowns or local transit, so you'd still need a 45 minute drive on each end to get from/to where ever you're actually going. It's a 2.5 hour drive door-to-door today, so now you've just got a three-seat journey where there was once a one-seat trip, to maybe shave 30 minutes off journey time.
Moreover, there's no technology that could build such a train. LA to to San Diego is 200 kilometers. It would almost certainly need to make stops like Anaheim, Irvine, Oceanside, etc.. Oh, by the way, there's a mountain range between the two. Even state-of-the-art HSR would struggle to maintain 200 km/hour over the entire route. So now your train ride is an hour, and you've actually saved no time.